High performance tribological coatings on a secondary cast Al–Si alloy generated by Plasma Electrolytic Oxidation

Abstract

Due to their outstanding properties, including low density or high-strength-to-weight ratio, cast Al–Si alloys are attractive materials. Nevertheless, their low wear and corrosion resistance still remain a critical issue for several applications. The present work is focused on the obtention of PEO coatings on a secondary cast Al–Si alloy (EN AC-46500) and the in-depth study of the properties derived from the use of two developed aluminate-based electrolytes.All the obtained PEO coatings have been characterized in terms of their thickness and roughness, morphology, and composition. Reciprocal wear tests have been performed in order to evaluate the tribological behavior of the PEO layers, while their anti-corrosion properties have been analyzed throughout Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy.Our findings suggest that the aluminate-based electrolytes led to an increase in coating thickness of density, while providing a notable improvement on the surface hardness in comparison with the uncoated Al–Si alloy. All the PEO coatings tested exhibited excellent wear resistance and an improved anti-corrosion behavior compared with the uncoated Al–Si alloy. Furthermore, K2TiF6-containing electrolyte promoted the obtention of PEO coatings that provided the highest protection against wear and corrosion to the cast Al–Si alloy treated.